The present invention relates to a heat sink assembly and a method of assembling a heat sink to an electronic device. The invention particularly relates to a heat sink assembly that includes a clip which compresses a heat sink against an electronic device.
Electronic devices generate heat during operation. Thermal management refers to the ability to keep temperature-sensitive elements in an electronic device within a prescribed operating temperature.
Historically, electronic devices have been cooled by natural convection. The cases or packaging of the devices included strategically located openings (e.g., slots) that allow warm air to escape and cooler air to be drawn in.
The advent of high performance electronic devices, such as processors, now require more innovative thermal management. Each increase in processing speed and power generally carries a xe2x80x9ccostxe2x80x9d of increased heat generation such that natural convection is no longer sufficient to provide proper thermal management.
One common method of cooling electronic devices includes thermally coupling a heat sink to the package of the electronic device. A typical heat sink includes protrusions, such as fins or pins, which project from a body of the heat sink. The protrusions give the heat sink a larger surface area such that the heat sink dissipates a greater amount of thermal energy from the package into the surrounding environment. Heat sinks are fabricated from materials with high thermal conductivity in order to efficiently transfer thermal energy from the electronic device package.
The heat sinks are typically mounted to the electronic devices by using adhesives, screws, and/or bolts. Another common method uses one or more clips to secure a heat sink to an electronic device.
FIGS. 1-5 illustrate a prior art heat sink assembly 10. Heat sink assembly 10 includes a heat sink 20, clip 30 and electronic device 40. Electronic device 40 is mounted to a frame, such as socket 50. Socket 50 is attached to a substrate, such as printed circuit board 51 (see FIGS. 4 and 5). Clip 30 compresses heat sink 20 against electronic device 40 and is typically in the form of a bent wire that includes two legs 32 and an elongated central portion 34 extending between the legs 32. Each leg 32 is substantially perpendicular to central portion 34 and extends from central portion 34 in an opposite direction to the other leg 32.
The central portion 34 of clip 30 extends between protrusions 28 on heat sink 20. Clip 30 is assembled to socket 50 by maneuvering legs 32 under a pair of tabs 52 that are positioned on opposing sides of socket 50. Legs 32 deflect elastically as they are moved under the tabs 52 generating a torque around the central portion 34 of clip 30. The torque compresses the central portion 34 of clip 30 against heat sink 20, which in turn compresses heat sink 20 against electronic device 40. Compressing heat sink 20 against electronic device 40 reduces the thermal resistance between heat sink 20 and electronic device 40.
FIG. 4 illustrates the proper position for heat sink 20 relative to electronic device 40. Heat sink 20 includes a contact surface 21 that should be engaged with electronic device 40 over the entire contact surface 21.
Mechanical shock or vibration during transportation and handling can cause heat sink 20 to shift relative to electronic device 40. FIG. 5 illustrates a case where heat sink 20 has shifted relative to electronic device 40. A portion 22 of the contact surface 21 on heat sink 20 is no longer fully engaged with electronic device 40. This situation is undesirable because anything less than full contact between the contact surface 21 on heat sink 20 and electronic device 40 renders heat sink 20 less effective in conducting thermal energy from electronic device 20.
There is a need for a heat sink assembly and method that securely attaches a heat sink to an electronic device, especially when subjected to mechanical shock or vibration. The clips that are presently used to fasten heat sinks to electronic device packages are unable to adequately secure a heat sink to an electronic device package under such circumstances.